1. Field of Invention
The present invention relates to clip-on nuts and, in particular, a device for enabling a panel to be coupled to a support structure.
2. Description of Prior Art
The term clip-on nut will be used in this disclosure to refer to the present invention as well as the entire general field. Other terms in use are "C-type fastener"; "U-shaped clip-nut"; "J-fasteners" and the like which describe the general shapes. Clip-on nuts are usually made of spring steel or hardenable steel formed from thin sheets by punching and bending and usually followed by heat treatment. An earlier form of clip-on nut is described in U.S. Pat. No. 2,062,685 to G. A. Tinnerman. In recent years, the field has specialized to include wide range clip-on nuts capable of emplacement on a wide range of panel thicknesses, such as shown in U.S. Pat. No. 3,358,729 to R. A. Munse.
Clip-on nuts usually slide onto the edge of a work panel with a portion on each side of the panel to place a nut element in line with a hole. Sometimes a clip-on nut is attached through a slot in a work panel rather than at an edge.
They are used in any application where access is limited so that manually holding a nut behind the hole is difficult or impossible. They are also used where it is desired to provide self retention of the nut on the work panel without riveting or other expensive means. Common applications are in automobiles, appliances, and aircraft.
Most clip-on nuts are located in a line with a hole by eye or by a piece that extends into the hole such as in U.S. Pat. No. 3,414,035 to R. A. Munse. Rapid emplacement and accurate locating on a work panel are important features of any clip-on nut. Low cost is another important feature.
The clip-on nut disclosed in U.S. Pat. No. 3,927,707 comprises a threaded nut element which has attached to it two arms extending in a plane which is radial to the longitudinal axis of the nut element at pre-determined angles. The arms are bent back upon themselves to form upper and lower opposed portions, the space between them adapted to receive a work panel. Protrusions extend into the space from the lower portion of the arm, and bent guide tabs extending away from the arms to facilitate emplacing the clip-on nut on a work panel are also provided.
U.S. Pat. No. 4,074,491 to Bell et al discloses a clip-on nut, or spring clip, having a resilient material molded to the interior surface thereof. Each of the legs of the U has an aperture and the apertures are aligned for receiving a bolt therethrough. The resilient material is integrally molded into a bushing within each of the apertures, the bushing including a projection of resilient material which, when the clip is slipped onto the support structure having a mating hole, allows the projection on the apertured legs to extend into the opening, thereby forming an interlocking engagement with the hole for retention of the clip.
Another clip-on nut which has been commercially available has a vertically extending cylindrical projection formed on one leg of the U positioned adjacent to and in alignment with an aperture formed in the other leg. The vertically extending portion is used to guide the clip to an aperture formed on a work panel.
Although the clip-on nuts currently available have been used with various degrees of success, a major disadvantage is that they tend to scratch the metallic surface of the work panel which in turn provides a path for corrosion, the structural integrity of the assembled part thus being endangered. Although the resilient projections shown in the Bell patent device ma inhibit scratch formation in the support structure as the clip-on nut is being secured thereto, the necessity of molding a resilient material to the inner surface of the clip-on nut substantially increases the cost of fabrication thereof.
What is thus desired is to provide a clip-on nut designed to minimize scratching of the support structure surface and which is also simple and inexpensive to fabricate.